The present invention relates generally to inhibitors of arginase and their use for the treatment of pathological states. Two arginase isozymes (ARG-1 and ARG-2, denoted also as arginase I and II, respectively) exist in mammals, that hydrolyze arginine to ornithine and urea. Both enzymes catalyze the same biochemical reaction, but differ in cellular expression level, regulation and subcellular localization. ARG-1 is a cytosolic protein and ARG-2 is mainly localized in mitochondria (Jenkinson C P, Grody W W, Cederbaum S D. Comparative properties of arginases. Comparative biochemistry and physiology Part B, Biochemistry & Molecular Biology. 1996; 114(1):107-132).
The arginases are implicated in various pathological states. These include, without limitation, asthma, pulmonary hypertension, hypertension, T cell dysfunction, erectile dysfunction, atherosclerosis, renal disease, ischemia reperfusion injury, neurodegenerative diseases, wound healing, inflammatory diseases, fibrotic diseases and cancer.
Arginase expression and L-arginine depletion is known immune-suppressive pathway of the mammalian immune system (Munder M. Arginase: an emerging key player in the mammalian immune system. Br J Pharmacol. 2009; 158(3):638-651). L-arginine deficiency down-regulates expression of T cell receptor (TCR) ζ chain, a key signaling element of the TCR, thereby impairing T cell function (Rodriguez P C, Zea A H, Culotta K S, Zabaleta J, Ochoa J B, Ochoa A C. Regulation of T cell receptor CD3zeta chain expression by L-arginine. J Biol Chem. 2002; 277(24):21123-21129). Depletion of L-arginine from the microenvironment leads to an arrest in T cell cycle progression, inhibition of IFN-γ production, and blocking of signaling through the T cell receptor.
Arginases are mainly produced by myeloid-derived suppressor cells (MDSC) that are highly enriched in the tumor-bearing state (Bronte V, Serafini P, De Santo C, Mariango I, Tosello V, Mazzoni A, Segal D M, Staib C, Lowel M, Sutter G, Colombo M P, Zanovello P: IL-4-Induced Arginase 1 Suppresses Alloreactive T Cells in Tumor-Bearing Mice J Immunol 2003; 170:270-278). Induction of arginase pathway is an important mechanisms involved in the evasion of anti-tumor immunity. High arginase activity has been observed in patients with various malignancies, both in blood and within tumor mass.
It was shown that T cell functions are restored and tumor growth is inhibited upon inhibition of arginase of tumor-associated MDSC or tumor-infiltrating CD11b+Gr-1− mature myeloid cells in various murine tumor models (Rodriguez P C, Quiceno D G, Zabaleta J, et al. Arginase I production in the tumor microenvironment by mature myeloid cells inhibits T-cell receptor expression and antigen-specific T-cell responses. Cancer Res. 2004; 64(16):5839-5849). Depletion of the myeloid suppressor cells re-establishes T cell receptor- and costimulation-induced T cell activation (Zea A H, Rodriguez P C, Atkins M B, et al. Arginase-producing myeloid suppressor cells in renal cell carcinoma patients: a mechanism of tumor evasion. Cancer Res. 2005; 65(8):3044-3048).
Arginase was shown to participate in the suppression of tumor-infiltrating lymphocytes in patients with prostate carcinoma (Bronte V, Kasic T, Gri G, et al. Boosting antitumor responses of T lymphocytes infiltrating human prostate cancers. J Exp Med. 2005; 201(8):1257-1268), non-small cell lung carcinoma (Rodriguez P C, Quiceno D G, Zabaleta J, et al. Arginase I production in the tumor microenvironment by mature myeloid cells inhibits T-cell receptor expression and antigen-specific T-cell responses. Cancer Res. 2004; 64(16):5839-5849) and multiple myeloma (Serafini P, Meckel K, Kelso M, et al. Phosphodiesterase-5 inhibition augments endogenous antitumor immunity by reducing myeloid-derived suppressor cell function. J Exp Med. 2006; 203(12):2691-2702). Not only MDSC but also dendritic cells (DCs) have been shown to suppress CD8+ T cells and antitumor immune responses through ARG-1 production (Norian L A, Rodriguez P C, O'Mara L A, et al. Tumor-infiltrating regulatory dendritic cells inhibit CD8+ T cell function via L-arginine metabolism. Cancer Res. 2009; 69(7):3086-3094).
Given the role of arginase in various pathological states and their role in chronic inflammation and suppression of anti-tumor immunity, the present invention provides novel boron-containing compounds as inhibitors of arginase activity, as well as methodologies for using these compounds as therapeutics.
Numerous boron-containing arginase inhibitors are well-known from the literature. One of such inhibitors is 2(S)-amino-6-boronohexanoic acid, as described in WO9919295A1, published on Apr. 22, 1999, and in WO08061612A1, published on May 29, 2008. Besides, WO11133653, published on Oct. 27, 2011, and WO13059437, published on Apr. 25, 2013, describe a number of alpha-amino acid derivatives bearing a terminal B(OH)2 group and a spacer, usually being a 1,3-cyclobutylene moiety. Mono- or polycyclic boron-containing amino acid compounds suitable as arginase inhibitors are described in WO12058065, published on May 3, 2012. Another related patent application publications are WO10085797 of Jul. 29, 2010, WO13158262 of Oct. 24, 2013, and WO12091757 of Jun. 5, 2012.
Significance of substitution at the alpha center of 2-amino-6-boronohecanoic acid for the inhibitory potency of arginase I and arginase II inhibitors has been discussed (Golebiowski A., et al. 2-Substituted-2-amino-6-boronohexanoic acids as arginase inhibitors. Bioorg. & Med. Chem. Lett., 2013; 23:2027-2030).
There is a need to investigate the inhibition of arginases, and to discover treatments for conditions associated with elevated expression of arginases, such as asthma and allergic responses. In particular, there is a need to explore new molecular scaffolds that effectively inhibit arginases and, therefore, can act as therapeutic agents for the treatment of these conditions.
The present inventors arrived at small molecule arginase inhibitors that proved to be very active, and exhibited superior pharmacokinetics.